Oriented strand board (also known as “OSB”) is an engineered wood product formed by layers of flakes or strands of wood placed in specific orientations and bound together. It is generally manufactured in mats from cross-oriented layers of thin, wood flakes compressed and bonded together with wax and resin adhesives. The mats are typically laminates comprising a plurality of layers built up with the external layers aligned to give the mats strength in desired directions. The number of layers of each mat is determined partly by the desired thickness of the mat and may be limited by the equipment used in the manufacturing process.
In a process of manufacturing the mats, the flakes are placed in a press having the ability to apply heat to the flakes. The flakes are compressed and bonded together by heat activation and curing of a resin that has been coated on the flakes. Individual panels are then cut from the mats to produce OSB panels of desired sizes. Also in the manufacturing process, the wood flakes may be treated with various compounds to inhibit infestation by insects and/or to discourage the growths of molds and fungi. Treatment may be either before the cutting of the mats into OSB panels or after.
Different qualities in terms of strength and rigidity can be imparted to the OSB by changes in the manufacturing process. Although finished OSB panels have no internal gaps or voids and are typically water-resistant due to the wax and resin adhesives, they generally require additional treatment to achieve impermeability to water, particularly when the OSB is for exterior use. Finished OSB panels have properties that are similar to plywood, but the panels are generally more uniform in construction. The most common uses of OSB are as sheathing in walls, floors, and roofs.